Method of hardening brake drums of malleable-iron disk automobile wheels



May 7, 1929. T. R. DAVIS 1,711,835

METHOD OF HARDENING BRAKE DRUMS OF MALLEABLE IRON DISK AUTOMOBILE WHEELS" Flled May 17, 1926 INVENTOR: Th0ma6R.Z)ar/i *M ATTORNEYS.

- hgat Patented May 7, 1929. I

THOMAS DAVIS, OF'IFAIRFIELD, CONNECTICU 'TL mnrnon or HARDENING BRAKE mums WHEELS.

Application and May 17,

This invention relates to improvements in' the'method of manufacturing malleable iron disk automobile wheels, and relates more particularly to the method of hardening the brake drum portion of the wheel so as to insure it withstanding the required amount of wear to which it may be subjected.

By way of introduction '1 will first briefly review the method producing malleable. iron,

to which my invention relates. Commercial malleable iron when cooling from the liquid state in which it is cast, and before the annealing process, is known as white iron.

This iron has ,a characteristic silvery white fracture and consists of an alloy of; iron, carbon, silicon, manganese, sulphur and phosphorus. These elements are so proportioned that the casting as it cools contains no free carbon, that is all thecarbon is combined with the ironas iron carbide and the resultant structure is a fairly homogeneous mixture of cementite and pearlite. Theiron carbide of this mixture, however, is not in a stable condition, but under the influence temperature, which for commercial white iron is about 137 5 deg. Fah., extending over a number of hours-will break down into its components of carbon and iron. This-carbon, however, which is precipitated from a solid structure does not have the facility of collecting together in large flakes or globules such as is characteristic of the carbon which is separated from a molten solution and which is noticed in the fracture of gray iron. The carbon, or'more properly graphite, which separates from the white iron when it is subjected tora. heat in excess of its critical temperature and held for a num- 40 her ofhours, is of a very finely pulverized condition and is scattered uniformly throughout the mass of the casting. The

resultant structure may be considered as an extremely dense sponge with its pores filled.

with temper carbon.

After the precipitation of carbon has been completed in the annealing furnace, commercial 'malleable iron is produced. The carbon in this state, that is temper carbon, again is not stable when subject to high but, will go back into solution with the iron forming an iron carbide." The amount of the iron carbide or, in other words, the amount of carbon going into solution with the iron, being in proportion to the temperaof a temperature in excess of the critical .192 6. Serial m. 109,605.

ture as the combination of carbon and iron with arising temperature follows a definite curve. The combination of carbon and iron when malleable iron is heated, however, takes place almost instantaneously. I propose to take advantage of this phenomenon in case hardening the surface of the mal-;

leable iron brake'drums as will later be more fully explained. i In the accompanying drawi'ngs: Fig. 1 shows a plan view of an apparatus by means of which my improved method of hardening the brake drums of cast-metal wheels is carried out; f F'g. 2 is across sectional view, on'a reduced scal -taken on line 2 -2 of Fig. 1;

Fig. 3 shows 'a' cen tral vertical sectional ;view ofsa part of a malleable iron djsknuto mobilewhcel illustrating the original thickness of the brake drum; and

Fig. 4 showsa somewhat similar sectional or mALLEaBL E-InoN Disk nurouonrtr.

view of a wheel, the brake drum being thin-- ner than that shown in Figs. ,1 and 3'having been turned down, and illustrating the. ap-

plication of heat to the inside of the brake dllcllm instead of the outside as in Figs. 1 an 2;

1n illustrating my invention I have shown a type of automobilewheel, covered by a recently obtained U. S. Letters Patent. This wheel, as will be seen, is formed of a single malleable casting and includcsa hub 6, an integral ribbed disk portion 7, an au- .nular flange 8 and an integral annular cylindrical brake drum member 9. 'lhewheel 1s obviously formed of very thin, conse quently relatively light, though strong malleable iron and in the usual manner-of producing this kind of casting as hereinbefore set forth.

a It is obviously important thatthe brake drum which, as before stated, is formed integral with the disk portion of the wheel, should first be made concentric withthe axis of the wheel and secondly must be sufiiciently hard to resist the extreme abrasion to which it is subjected by reason of the application of the brake. In the production or my wheel I therefore originally form the brake band portion of the wheel somewhat thicker (as suggested by Fig. 3) than is actually necessary and turn the s'aine'down as at 10 either from the inside or outside according to which side the braking ele n lent is to be applied, said machining off of the metal being preferably done after the wheel as a whole has been heat treated as in the art of making a malleable iron casting. This machining operation serves to remove the decarbonized skin of the brake drum and presents a surface that is im regnated with temper carbon which will be immediately combined with the iron with the application of heat in excess of the critical temperature, thus insuring a harder brake drum surface than would be possible to obtain with the decarbonized skin on the drum.

In the accompanyin drawing I have shown a simple-form 0 machine by means of which my invention may be carried out yet it will be obvious that other means or mechanisms may be employed to equally as good advantage and without departing from the spirit of the invention. I find that malleable. iron automobile wheels of my improved type having integrally formed brake drums, can be best treated in accordance with my invention when mounted to rotate and by employing both heat and water-as a means of hardening the brake drums. I

' have therefore devised a water tank 11 u on 3 sition so that the flame therefrom will be directed across the width of the surface of the which vis mounted a bearin 12 in whic a portion of an arbor 13 is journaled to ro-' tate. The outer end portion of said arbor is further journaled in a bearing 14 which may be securedto .the floor, and the outer end of the arbor is provided with a ulley 15 by means of which the arbor and w eel may be rotated, The inner end .of the arbor 13 is tapered as at 16, threaded andprovided with a nut 17 for the detachable mountin of the malleable iron automobile whee The wheel may be thus mounted to be rodruin. This nozzle is mounted upon the inner end ofa hollow arm 19 carried in a member 20 adjustably mounted in a standard 21 that is slidably mounted in a) guideway 22 in which is positioned an adjustmg screw 23 for moving the nozzle to and from the brake drum. a, The guideway 22 is mounted for pivotal adjustment upon a support 24 as at 25, and is provided with 'an ad'usting screw 26 whereby the ixmer end of.t e said guidewa and nozzle may be raised and lowcred an best sitioned with respect to the particular sty e and size of brake drum to be hardened. The nozzle is provided with fuel supply pipes 27 and air pipes 28 whereby the required mixture of fuel may be provided. A water pipe 29 is also connected with the burner for-cooling purposes.-

For convenience of illustration, I have shown this pipe connected with the main water supply pipe 29 for the water nozzle 30 positioned within the brake drum and substantially opposite the position of the ox -acetylene nozzle;

11 Fig. 4 the relative positions of these two nozzles are reversed from that shown in Fig. 1, the oxy-acetylene nozzle being on the the tank of water into which the wheel and drum revolves immediaely upon leaving the flame.

The flame would not have time to heat more than just the surface of the metal before the metal would be plunged into the water and quenched. The water from the spray flows over the entire surface of the drum as it passes the flame and has the effect of always keeping one side of the drum opposite. the flame from a dangerous heat.

This prevents any warping .of the drum and is an insurance against the drum becoming heated throughout in any one spot above the critical temperature, causing a plane of brittleness.

The flame itself could be directed directly against the surface of the drum, or it mi ht be directed down or perhaps upward. e principle of the invention would be the same in all cases-that is, the-surface of the drumwould be flashed above its critical temperature while the back ofthe drum would-be held to normal by "application of water. This gives a .very hard surface to the drum which we can regulate to any depth desired by the amount of heat applied and. the amount of time that this application will last. At the same time, we maintain the body .of the drum in the same strong mal- Tleable condition as when it came from the annealing furnace.

Having thus described my invention,

Ill

whatI claim anddesire to obtain by Letters Patent is:

The herein described method of manufacturing a malleable iron automobile wheel, including a brake drum, which consistsin machining oif the outer periphery of the drum to remove the decarbonized skin of the brake drum and comprising a surface that is impregnated with temper carbon which will be immediately combined with the iron with the application of heat in ex-- cess of the critical temperature, directing a.

flame across the entire width, of the outer periphery of the drum heating the machined surface to a temperature in excess of the critical temperature While the drum is rotating, and simultaneously directing a spray of water across the entire width of the inner I periphery of the drum directly opposite the point of application of heat to maintain the inner periphery opposite the flame from a dangerous temperature, and maintain the inner periphery of the drum at a temperature less than the critical temperature to prevent 10 warping of the drum.

Signed at Bridgeport in the county of Fair-field and State of Connecticut this 14t day of May, A. D. 1926. v

THOMAS R DAVIS. 

